The present invention relates to an improved process for welding a metallic conductor wire to a metallic conductor piece, by ultrasonic bonding. More particularly, the present invention relates to the construction of automobile alternator slip rings and the use of an improved ultrasonic welding process to produce a slip ring assembly.
According to one known practice, to make an ultrasonic weld the wire, or a part of the wire (an end or middle section), is placed in contact with one exterior side of the piece to which it will be welded to. Then a working side of an electrode of an ultrasonic generator is placed on the wire under a pressure of defined stress. Then, the wire is subjected to the effect of an ultrasonic vibration coming from the electrode for a defined time. When the electrode is removed, the welded portion of the wire is flat due to the stress and it strongly adheres to the piece.
However, to obtain the above desired result, the wire, during the welding process, has to be held fixed with respect to the piece in order to avoid relative movement between them during the "vibrative oressure" which is generated. In addition, since the welded part of the wire is flat, the wire presents a potentially brittle surface at the junction of the aforesaid flat welded part with its unflat and unwelded part(s).